If you have a smartphone or iPhone, there is an ap called "Happy Hours" which covers a lot of major markets across the U.S.
It knows your location (if you allow it) as well as the local time and will list happy hours that are taking place at that time. You can drill down to find what specials they offer, filters, distance from your present location, map, etc.
There are a ton of very good deals in Vegas; both inside and outside the casino environment.
Hope this helps!
Dan